P – BLOCK ELEMENTS MCQs – 3

1)Nitrogen is a relatively inactive element becausea)Its atom has a stable electronic configurationb)It has a low atomic radiusc)Its electronegativity is fairly highd)The dissociation energy of its molecule is fairly high

2)Which one of the following substances is used in the laboratory for a fast drying of neutral gases?a)b)Active charcoalc)d)

3)When ammonia is passed over heated CuO, it is oxidised toa)b)c)d)

4)One would expect a proton to have a very largea)Chargeb)lonization potentialc)Hydration energyd)Radius

5)The ozone molecule isa)Paramagneticb)Linearc)Diamagneticd)Can be represented by a single structure

6)Pure nitrogen can be prepared froma)b)c)d)

7)Ozone belongs to which group of the periodic table?a)14b)15c)16d)None of the above

19)About 20 km above the earth there is an ozone layer. Which one of the following statements about ozone and the ozone layer is truea)The o\zone layer is beneficial to us because ozone cuts out the ultraviolet radiation of the sunb)The conversion of ozone to oxygen is an endothermic reactionc)Ozone has a triatomic linear moleculed)The ozone layer is harmful to us because it cuts out radiation useful for photosynthesis

20)When SO2 gas is passed through cupric chloride solutiona)The solution becomes colourless, but no precipitate is formedb)A white precipitate is formed, but no colour change.c)No change takes placed)the solution becomes colourless and a white precipitate is formed

21)Which of the following statements about white phosphorus are not true ? a)It phosphoresces in airb)It burns when heated in airc)d)It can be stored in contact with air

22)Which statement is correct?a)Ozone is a resonance hybrid of oxygenb)Ozone is an allotropic modification of oxygenc)Ozone is an isomer of oxygend)Ozone has no relationship with oxygen

65)A gas which was formerly used as an anaesthetic in dental surgery isa)NOb)c)d)All the above

66)Hydrogen has three isotopes. The radioactive isotope has the mass numbera)3b)6c)2d)All the above

67)Semi water gas is a mixture ofa)b)c)d)None

68)An odd electron bond is not present ina)NOb)c)d)None of the above

69)Liquid oxygen isa)Colourlessb)Pale yellowc)Pale blued)Dark blue

70)Which of the following combines with Fe(II) ions to form a brown complex?a)b)NOc)d)

71)Which of the following colours is not associated with ozone?a)Pale Blueb)Bluec)Purpled)Green

72)Nitrogen can be purified from the impurities of oxides of nitrogen and ammonia by passing througha)Ammoniacal copper sulphate b)Conc. HClc)A solution of KOHd)None

73)Hydrogen can form bondsa)By losing an electron onlyb)By gaining an electron onlyc)By sharing an electron onlyd)All the above

74)Hydrogen can be obtained from watera)Only by electrolysisb)Only by the action with active metalsc)Only by the reaction with metal hydridesd)All the above

75)Which of the following on reaction with H2SO4, will not liberate hydrogen: Zn, Al2O3, Cu?a)b)c)d)Both Al2O3 and Cu

76)Oxygen is not evolved whena)Potassium chlorate is heatedb)Sodium peroxide reacts with waterc)Ammonium nitrate is heatedd)All the above

77)Out of MgO, BeO, SnO, which is/are amphoteric ?a)MgO and SnOb)BeO and MgOc)BeO and SnOd)SnO alone

78)Which of the following statements are correct?a)b)c)d)All the above

79)Which of the following metals Fe, Al and Ni become passive on reacting with conc. HNO3?a)Fe aloneb)Al and Fec)Ni and Ald)All the three

80)sp2-Hybridization is found in the structures ofa)b)c)d)both a and c

81)Which of the following is isoelectronic as well as having the same structure as that of N2O?a)b)c)d)

82)The molecule which has a pyramidal shape isa)b)c)d)

83)Which of the following oxides is the most acidic?a)b)c)d)

84)Orthophosphoric acid isa)Monobasicb)Dibasicc)Tribasicd)Tetrabasic

85)The number of P-O-P bonds in a cyclic metaphosphoric acid isa)Zerob)Twoc)Threed)Four

86)The hybridisation of the atomic orbitals of nitrogen in NO, NO, and NH area)b)c)d)

87)Which of the following forms of phosphorus is the most reactive?a)Red phosphorusb)Yellow or white phosphorusc)Scarlet phosphorusd)Violet phosphorus

88)Nitrogen can be obtained from air by removinga)Oxygenb)Hydrogenc)Carbondioxided)Oxygen, CO2 , and noble gases

89)Repeated use of which of the following fertilizers would increase the acidity of the soil?a)Ureab)Potassium nitratec)Ammonium sulphated)Super phosphate of lime

90)An element (X) forms compounds of the formula XCl3,X2O5 and Ca3X2, but does not form XCl5. Which of the following is the element?a)Bb)Alc)Nd)P

91)There is very little difference in acid strengths in the series H3PO4, H3PO3 and H3PO2 becausea)Phosphorus is not a highly electronegative elementb)The hydrogens in these acids are not all bonded to phosphorusc)Phosphorus in these acids exists in different oxidation statesd)Phosphorus oxides are less basic

92)Sodium pyrophosphate isa)b)c)d)

93)In the nitrogen family the H-M-H bond angle in the hydrides MH3 gradually becomes closer to 90Â° on going from N to Sb. This shows that graduallya)The basic strength of the hydrides increasesb)Almost pure p-orbitals are used for M-H bondingc)The bond energies of the M-H bond increasesd)The bond pairs of electrons becomes nearer to the central atom

94)Which oxide of nitrogen is a coloured gas?a)b)NOc)d)

95)Which of the following is a tetrabasic acid?a)Orthophosphoric acidb)Hydrophosphoric acidc)Metaphosphoric acidd)Pyrophosphoric acid

96)The basic character of the hydrides of VA (15) group elements decreases in the ordera)b)c)d)

97)Among the trihalides of nitrogen which one is most basic?a)b)c)d)

98)Which of the following species has the highest dipole moment?a)b)c)d)

99)Group 15 of the periodic table consists of N, P, As, Sb and Bi. On passing from N to Bi, the oxides of the elements with the general formula M2O3 becomesa)Stronger reducing agentsb)More ionicc)More basicd)More volatile

100)Which one of the following penta fluorides cannot be formed?a)b)c)d)

Answer :

Ans 1) d

Ans Desc 1)N2 molecule contains triple bond between N atoms having very high dissociation energy (946 kJ mol-1 ) due to which it is relatively inactive.

Ans 2) c

Ans Desc 2)Anhydrous CaCI2 is used for fast drying of neutral gases.

Ans 3) a

Ans Desc 3)2 NH3 + 3 CuON2+3 Cu+3 H2O.

Ans 4) c

Ans Desc 4)A proton (H+) being very small in size would have a very large hydration energy.

Ans 5) c

Ans Desc 5)Ozone is diamagnetic, because it has no unpaired electron in its structure.

Cyclic metaphosphoric acid has the structure shown below. Thus there are three P-O-P bonds

Ans 86) b

Ans Desc 86)No. of hybrid orbitals = Total no. of sigma bonds + lone pair of electrons. The no. of sigma bonds in NO, NO and NH are 2,3 and 4 respectively. So the hybridisation is sp, sp2 and sp3 respectively.

Ans 87) b

Ans Desc 87)White or yellow phosphorus is the most reactive form of phosphorus.

Ans Desc 90)N forms NCl3,N2O5 and Ca3N2. Nitrogen, which has no empty d-orbitals, cannot extend its covalency by more than three and hence does not form NCl5.Due to its small size and high electronegativity it can accept 3 electrons to form N3- ion (Ca3N2).

Ans 91) a

Ans Desc 91)There is little difference in the strength of these acids because phosphorus is not a highly electronegative element.

Ans 92) c

Ans Desc 92)

Ans 93) b

Ans Desc 93)The hybrids have a pyramidal or tetrahedral shape with a lone pair of electrons in one of the orbitals. The H-M-H bond angle is less than the original 109Â°28 tetrahedral bond angle (H-N-H in NH3 is 106Â°45) because of greater repulsion between a lone pair and a bond pair than between two bond pairs of electrons. Because the electronegativity of M decreases from N to Bi, the bond pair lies farther away from the central atom, and the lone pair causes greater distortion of the bond angle. Thus the H-P-H bond in PH3 is 94, while in AsH3 and SbH3 it is about 91.8Â°, and 91.3Â° respectively (closer to 90Â°). This suggests that the orbitals used for bonding are closer to pure p-orbitals.

Ans 94) d

Ans Desc 94)NO2 is a reddish brown gas.

Ans 95) d

Ans Desc 95)

Pyrophosphoric acid, H4P2O7 is tetrabasic acid.

Ans 96) c

Ans Desc 96)The availability of electrons on an atom decreases down a group because of increase in size. Hence the basicity of these hydrides decreases from NH3 to SbH3 due to the increase in the size of the atom from N to Sb.